Transporting tongs



United States Patent [72] Inventor l'lans Rlehner [56] References Cited [2" A I No ggz' gg UNITED STATES PATENTS [22] f DOB 23, 1968 2,620,219 12/1952 Novotney 294/118 3,125,370 3/1964 McGill 294/106 [45] Patented Dec. 8, 1970 3 363 929 l l 68 N l [73] Assign" E Bihubur AG. 9 e son 294/106 1 Basel, Switzerland Primary Examiner-Andres H. Nielsen [32] Priority Dec. 29, 1967 Attorney-Kurt Kelman [33] Netherlands [31] No. 67.17821 ABSTRACT: This invention relates to transporting tongs for transporting workpieces during the shaping thereof. The tongs comprise two pivotally connected tong arms, at least one of which is adapted to be opened and closed periodically. Further, one of the tong arms is subdivided into two portions, [54] TRANSPORTING TONGS the two portions being pivota lly interconnected. At the inter- 3 Cl l 4 Drawing Figs. connection of these two portions there 1s arranged an elast1c element. Thus with such an arrangement 1f the tong arms col- [52] US. 294/116, lide with an obstacle during the transporting of a workpiece, 294/115 the interconnected arm portions allow the tong arms to be [51] Int. B66c 1/42 deflected out of the path of the obstacle. When the tongs have [50] Field of Search 294/113, passed the obstacle the elastic member will permit the tong arms to return to their former position.

TRANSPORTING TONGS shaping station to the next. Under the influence of precisely adjusted control cams they engage the workpiece, hold it fast during the transverse movement of the carriage, and release it again-at the beginning of the new shaping operation, to return again to their initial location in their opened position.

It is repeatedly found that the tongs holding the'workpiece encounter an obstacle during transverse conveyance, for example an incompletelydischarged workpiece. The impinging tong arm, situated forwardly in the direction of the transverse conveying movement, is actedupon in the sense of a further closing movement. But since. the tongs are already fully closed, they will be deformed under the influence of the high transverse conveying forces unless a suitable safety device is provided.

It is true that the driving mechanism of the carriage is generally provided with a safety device which switches off the machine when a specific overload occurs. In view of the considerable masses involved and the consequently resulting force for which the carriage safety device must be adjusted, it is hardly possible to prevent deformation to the tong arms.

According to the present invention there are provided transporting tongs comprising two tong arms which are pivotally connected to each other, a tong arm transporting carriage on which the tong arms are mounted, a control mechanism for periodically moving at least one of the tong arms to open or close the tongs, at least one of the tong arms being subdivided into two pivotally connected arm portions, and an elastic element beingiarranged at the interconnection of the two subdivided arm portions to thereby allow deflection of the lower arm portion relative to the upper arm portion in opposition to the elastic member if the tong arms collide with an obstacle during transportation of the tongs.

An illustrative embodiment of the invention will now be described with reference to the accompanying drawings, in

which:

FIG. l shows a diagrammaticand partly sectional view of transverse conveying tongs after gripping a workpiece,

FIG. 2 shows a perspective view of the tongs apparatus,

FIG. 3 shows a section taken on the plane l-I of FIG. 1, and

FIG. 4 shows the tongs according to FIG. 1 shortly after impinging on an obstacle.

FIG. 1 shows diagrammatically, and omitting nonessential component parts, a set of tongs designated generally by the reference numeral 1, and comprising two tong arms 2 and 3. The tong arm 2 is connected rigidly to a shaft 4 which is mounted in a carriage 6 which is capable of moving to and fro in the direction of the arrow 5. The shaft 4 extends through the carriage 6 and comprises at the side of the carriage remote from the tongs a crank arm 7 (FIG. 2). Fixed rigidly to the crank arm 7 is a pin 8 which at one end carries a roller 9 which is arranged below a driving bar 10. The driving bar 10 moves under the influence of a cam disc in a continual rhythm in the direction of the arrow 11 upwards and downwards, this movement being transmitted through the parts 9, 8, 7 and 4 to the tong arm 2. Therefore, when the bar moves downwards, the arm 2 is rocked in the sense of an opening movement of the tongs.

The other tong arm 3 is connected rigidly to a pivot pin 12 mounted rotatably in the carriage 6. The two tong arms 2 and 3 are connected positively to one another by means of toothed segments 13 and 14 respectively, so that when there is a pivoting movement of the tong arm 2, the tong arm 3 must also move. The closing movement'of the tong arms is effected by a helical spring 15 which acts on the arm 3 and which is anchored to the carriage 6 and closes the tongs as soon as the position of the driving bar 10 allows this.

The carriage 6 is mounted slidably on a slide rail 16 (FIG. 2) and is driven by a mechanism not shown in the drawings, e.g. a sliding crank gear.

According to FIG. 1, the tongs l have just gripped a press workpiece 17 which is now to be transported from one shaping station to the next. The tongs therefore move with the carriage in the direction of the arrow 18. Then, if an unforeseen obstacle is encountered in the path of the tongs, for example an incompletely discharged workpiece, the tongs stick thereon and will be deformed or may even completely destroyed because of the action of the powerful transverse conveying forces of the carriage. In order to prevent this risk, the tongs I have a safety arrangement which will be described hereinafter.

The tong arm 2 is subdivided into two arm portions 19 and 20 respectively. The lower arm portion 20 of the arm 2 at its upper end 21 projects into an appropriate recess in the upper arm portion 19, in which it is pivotably mounted by means of a pin 22. The upper end of the lower arm portion 20 is subdi vided, as FIGS. 1 and 4 show, into two contact surfaces 23 and 24 which are situated at an angle relatively to one another. In FIG. I the contact surface 24 is situated directly below a leaf spring 25 which is fixed on the upper arm portion 19 and above which a recess 26 is provided in the arm portion 39. The leaf spring 24 thus bridges the recess 26 and bears only with its edge portions, so that its central portion can escape into the interior of the recess 26 under'the influence of an upwardly acting force.

Then, if during their transverse conveying movement, which takes place in the direction of the arrow 18, the tongs impinge on an obstacle, e.g. an incompletely discharged workpiece 27, the lower arm portion 20 pivots-over when a specific force occurs, the value of which can be set at the leaf spring 25. The leaf spring 25 is pressed upwards into the recess 26 by the transition edge of the two contact surfaces 23 and 24 until the tong arm portion 20 has reached the position shown in FIG. 4. Since the other tong arm 3 has also been rotated by means of the toothed segments I3, 14, the transverse conveying tongs a short time after impinging on the workpiece 27 take up the position shown in FIG. 4.

Unallowable stressing of the tong arms before the yielding position shown in FIG. 4 is reached, this being at the same time the end position of the transverse slide, could not occur. The interval of time between the encounter of the tong arm 2 with the workpiece 27 and the impingement of the press slide on the displaced arms is adequate for switching offand braking the machine, which, it is found, takes about a crank angle.

The example of embodiment described hereinbefore can be varied by the person skilled in the art in many respects without thereby departing from the framework of the present invention. Instead of the leaf spring 25 cooperating with the recess 26 it would readily be possible to use another elastic element which permits the pivoting over of the tong arm portion 20 and yet would secure this portion in its particular stable position at the time. Also, the pivotable connection between the two tongs arm portions 19 and 20 could differ considerably from that shown in FIG. 3, and for example could be made such that the upper end of the portion 20 is forked and fixed pivotably to a pin arranged on the portion 19. With this arrangement, preferably two diametrically oppositely situated leaf springs or a set of cup springs would be used laterally of the aforesaid pivot pin.

The recess shown in the drawings is also in no way absolutely necessary. Instead of a single leaf spring it would be possible in that case to use an elastically compressible spring assembly which can be compressed during the swinging over operation, to expand again subsequently.

It is also possible to provide any desired snap fastening devices which hold the arm in its straightened position by positive engagement etc.

When pivoting over into the position shown in FIG. 4, the surface of the tongs arm portion 20 adjoining the workpiece 17 must carry out a relative movement in relation to this workpiece. In contrast to the tong arm 3 the arm portion 20, therefore, does not have any accommodating groove for the workpiece 17.

lclaim:

l. Transporting tongs comprising two tong arms, said tong. arms being pivotally connected to each other; a tong arm transporting carriage, said tong arms being mounted in said carriage; a control mechanism, said control mechanism being adapted to periodically move one of said tong arms to open or close said tongs, one of said tong'arms being subdivided into upper and lower arm portions, said upper and lower arm portions being pivotally interconnected; and an elastic element, said elastic element being arranged at the interconnection of said two subdivided arm portions to thereby allow deflection of said lower arm portion relative to said upper arm portion in opposition to said elastic element if the tongarms collide with an obstacle during transportation of the tongs.

2. Transporting tongs according to claim 1 whichincludes a pivot pin; said lower arm portion being pivotally mounted on said upper'arrn portion by means of said pivot pin.

3. Transporting tongs according to claim 2 whichincludes a leaf spring and a recess on said upper arm portion into whichsaid leaf spring can yield; the upper face of said lower arm portion having two surfaces, said two surfaces adjoining one another and being arranged at an angleto one another, one of said surfaces in the normal position of said armportion abutting said leaf spring. 

